| الوصف: |
The ecology and structure of a population of white-tailed ptarmigan (Lagopus leucurus leucurus), residing during the summer near Logan Pass, Glacier National Park, were studied from early June to mid-September, 1959-62. Although ptarmigan were observed in a wide variety of habitats within the alpine zone, they showed a preference for areas having moderate rock cover, plentiful snow or water, and short, young vegetation. During the breeding season, 21 males and 14 females used the study area (7.08 acres of ptarmigan habitat). Territorial males returned to the same sites year after year and occasionally had the same mates. Yearling males rarely established and mated in their first year, but yearling females bred successfully. Females occasionally returned to the same breeding areas. Few females born on the study area returned to it, but many males did. Clutch size averaged 5.2 eggs (range 3-9). Nest parasitism was rare. Renesting occurred occasionally in phenologically early years. The percent of successful females varied from 35 to 82. Poor success was often caused by inclement weather. Hatching success was 85.5 percent. Brood size at flight age ranged from 3.25 to 3.47. Despite a large variation in natality, the size of the adult population at Logan Pass varied little. Average adult annual mortality was 29 percent, lower than that reported for other galliform species. Chick mortality was 35-44 percent by the time of dispersal. Mortality of immature birds was 63 percent by the following spring. A life table based on these average mortalities indicates a maximum life-length of 15 years, a mean longevity of 3.02 years, and an annual mortality rate of 42.1 percent. The Logan Pass population did not show the fluctuation in numbers reported for other species of ptarmigan and suggested for the tundra biome. The white-tailed ptarmigan (Lagopus leucurus) is perhaps the least known member of the grouse family (Tetraonidae) in North America. Prior to this study, few scientific investigations of this species had been made. Other aspects of this study were reported previously (Choate 1960a, 1960b, 1962, 1963). Many members of the grouse family (especially the ptarmigan) are known to fluctuate in numbers in a regular or cyclic fashion (Williams 1954). Ptarmigan populations showing these fluctuations were species other than white-tailed and came from arctic or subarctic habitats. To meet the need for further knowledge, a 4-year study was undertaken of the habitat and structure of a population of L. 1. leucurus residing on an area near Logan Pass, Glacier National Park, Montana. |
